With the progress of the times, the internet and mobile communication network provide massive functions and applications. A user not only can use a mobile terminal to perform conventional applications, such as use a smart phone to answer a call or call somebody up, but also can use the mobile terminal to browse a webpage, transmit a picture or play a game and so on.
With the increasing usage frequency of the mobile terminal, it is required to charge the mobile terminal frequently. In the related art, many power adapters charge the terminal with constant current, which is easy to implement, but cannot adjust the charging current according to actual situations of the terminal, thereby being inflexible. For example, if a voltage of a battery is too low, it is better to use large current to charge the battery quickly; if the voltage of the battery is very high, it is better to use lower current for charging, so as to avoid overcharge.